The present invention relates to a laser beam projection device and, more particularly, to an arrangement for permitting control of the orientation of a rotating laser beam.
A number of different laser beam systems have been employed in the past for surveying and construction applications to provide a rotating reference beam of laser light. This reference plane of light permits ready measurement of elevations and grades. Further, earth moving and other construction equipment may be fitted with laser light sensing devices which may be coupled through control systems to effect automatic or semi-automatic control of the equipment.
A laser beam projector typically employs a rotating reflective assembly which sweeps the beam in a horizontal plane or a selected tilted plane. Some prior art projectors have included visually readable tilt sensors and manually adjustable screws for orienting the projector in the desired attitude. Such a projector is disadvantageous in that its accuracy is dependent in part upon the skill of the operator in the initial adjustment of the orientation of the projector. Moreover, a subsequent unnoticed disturbance of the device can cause erroneous measurements to be taken.
Other prior art projectors have included electrical sensors which sense the orientation of the support platform and provide electrical signals used by a feedback control system. The feedback control system actuates electric motors to move the support platform into a position in which the sensors are leveled. When the reference laser plane is to be oriented at an angle to the horizontal, a grade motor for each desired axis is actuated by the operator to tilt the sensor with respect to the support platform. The feedback control system then reorients the support platform to bring the sensor provided for that axis back into its level position, thus tilting the frame by the desired amount. It will be appreciated that this requires a number of motors to accomplish the orientation of the sensors and the support platform along multiple axis, and is relatively complex and expensive.
Accordingly, there remains a need for an arrangement for use in a laser beam projection device which adjusts the orientation of a support platform in a simple fashion.